A typical airbag inflator comprises a steel or aluminum housing having walls of a thickness related to the gas production characteristic of the pyrotechnic utilized. Since the combustion pressure of a pyrotechnic is related to ambient temperature, the walls of conventional inflators are required to be relatively thick so as to contain the maximum gas pressure exhibited under high ambient temperature conditions. As a result, the inflator used in an inflatable vehicle occupant restraint system is generally the heaviest component of the system. However, if pyrotechnic overpressures can be regulated as opposed to being contained, the walls of the inflator can be relatively thinner and therefore lighter, a highly desirable attribute.
A typical state-of-the-art airbag inflator exhibits only the natural failure mode of the pressure vessel. Such failure modes generally evidence: 1) large variations in burst mode; 2) large variations in burst pressure; 3) frequent burst in a welded region or burst that is weld related; 4) burst at high dynamic pressurization rates; and 5) fragmentation at failure. Burst failures that result in fragmentation of the housing thereby endangering a vehicle occupant cannot be tolerated.